THE MISSION

It’s great to use a little fill-flash when taking portraits in daylight to lighten up people’s faces and reduce harsh shadows. However, DSLRs have a maximum flash sync speed determined by the amount of time it takes for the shutter curtains to physically move across the sensor – usually 1/200 or 1/250 sec, depending on your EOS DSLR. This means that, in bright conditions, you can’t shoot with flash at wide apertures at these sync speeds (eg f/2.8 at 1/200 sec) without ending up with overexposed images, and if you set a faster shutter speed, you’ll end up with a dark band across the frame as the moving shutter is captured in the image. An alternative option is to set a narrower aperture, but while the face will be brightly lit with the flash, the background behind the subject will be distractingly sharp.

What you need is a flashgun with a High Speed Sync (HSS) mode (all eight flashguns in last issue’s Super Test have this mode). HSS fires a pulse of low-power flashes for the duration of the exposure, rather than a single high-power burst, enabling you to set a much faster shutter speed than normal. This means you can open your aperture to blur your background for more dramatic portraits, because you can choose a higher shutter speed in daylight – such as f/2.8 at 1/1000 sec.

Another bonus of using HSS and faster shutter speeds is it can capture action portraits without a hint of motion blur in subjects.

STEP BY STEP: HOW TO SPEED UP YOUR FLASH

Set up your DSLR and flashgun to High Speed Sync mode for improved results

HSS mode dramatically reduces flash power as it fires a series of pulses of light. We started at 1/4 power with the flash on a stand two metres from our subject for a good exposure in bright sunshine. Avoid using diffusers as this reduces flash power further.

You’ll need specialist triggers if you want to fire your flashgun off-camera for more creative lighting. We used PocketWizards as they work with HSS, using a Mini TT1 transmitter on our DSLR’s hotshoe, with the flashgun on a Flex TT5 transceiver on a stand.

LIGHTMETER FOR FLASH

QUICK TIP!

For vertical portraits, if you’re firing a flash off-camera, position your flash on its side to light the entire face and body

Having trouble setting your HSS flash power for a good exposure? The clever Sekonic SpeedMaster L-858D light meter can measure the HSS output for precision flash exposure control. Incorporating flash duration measurement for the first time in a multifunction light meter, the new L-858D provides the flash data to help you calculate proper ambient-flash exposures for better-lit shots.